There is a series of applications in which an infinite adjustment option is desirable, for example, in the case of the adjustment option for a skylight, bringing window areas into a ventilation position, other ventilation flaps also being similarly movable, pivoting flaps on cooker extractor hoods or the like.
An extremely wide range of use of adjustment mountings of this type resides in the raising and lowering of an adjustable head or leg part of a bed, a couch, an armchair or the like. Mountings of this type, which frequently have toothed racks, are disclosed, for example, in DE-C-41 29 496, DE-C-22 62 947, DE-A-23 30 442, DE-A-38 02 962, DE-C-39 13 821 or EP-A-0 538 577, to name just some examples, and German Utility Model 77 04 457 shows the sliding mechanism without toothed racks.
An essential feature of the known solutions as furniture mountings is that, for example, the head part of a bed can only ever be raised in the incremental steps of the toothed ratchet rod or in notches made in guide elements. Bracing and fixing take place in a step sequence in each case. The solutions are envisaged such that when a maximum adjustment is reached, this position is exceeded via special mountings and devices in that the notches can be guided beyond the individual recesses into the lower dead center position in order once again to be able to bring about the stepwise raising.
The object of the present invention is to make infinite raising possible while retaining the return from the upper dead center position into the lower dead center position after the former has been reached.
Using a device of the type described at the beginning, this object is achieved according to the invention by means of two toothed wheels which run along a toothed rack, are guided in a cage or the like and whose spacing apart can be moved by means of the rod from a position locking the teeth of the toothed wheels against one another into a position which disengages the teeth.
The combination of a toothed rack having two toothed wheels which are guided on it and run along it and whose spacing apart can be influenced by the telescopic rod makes it possible for the telescopic rod to take up any position desired between a first dead center position and pull-out dead center position, in such a manner that adjustment steps no longer have to be kept to.
Refinements of the invention emerge from the subclaims, it being particularly expedient if the toothed wheels are guided in the interior of a housing, at least part of one housing wall being designed as a toothed rack.
This integration of the toothed rack directly into the housing guiding the toothed wheels ensures a very compact and simple design.
A further, simple design solution is if on the cage one toothed wheel axis is guided in a positionally fixed manner and one toothed wheel axis is guided such that it can be displaced in the pull or push direction, the pull and push being applied by means of the adjustable rod.
The displaceable toothed wheel axis can be guided in an elongated hole or slot in the cage, at least one dog, which can be overcome using an increased pulling or pushing force, being assigned to the path of movement of the toothed wheel axis.
This dog has the result that that toothed wheel which can be moved out of engagement initially positions itself with its axis against this dog in order to make it possible for the pull rod to be displaced from the lower dead center position into the pulled-up dead center position. If the upper dead center position is reached, a further force is applied, the dog is overcome and the toothed wheel is thereby permanently disengaged from the toothed wheel guided in a stationary manner in the cage, with the result that pivoting back from the upper dead center position into the lower dead center position is possible.
In this case, it is advantageous if, as the invention likewise envisages, the cage or the toothed wheel guide protrudes to such an extent over the toothed wheels that in the one pull-out position (upper dead center position) of the telescopic rod, the cage initially positions itself against the housing wall and in so doing makes possible the further path of adjustment of the movable toothed wheel axis via the telescopic rod. As already mentioned above, this path of adjustment comprises overcoming the latching dog and obtaining a return run.
The housing and/or the toothed wheels and/or the telescopic rod are advantageously made of plastic, for example polyamide, it also being possible for other materials to be provided for some elements.